Ferromagnetic alloy materials, such as Terfernol-D, have been utilized in magnetostrictive applications requiring high strains of 1500 ppm for example. A main drawback associated with some applications of magnetostrictive materials resides in exertion of mechanical stresses exceeding approximately 10 MPa for example, to achieve high strains.
It is presently known from previous studies that magnetic annealing treatment of magnetostrictive alloy material, helps remove certain imperfections therein and achieve a more preferential distribution of magnetic moments for delivery of larger magnetostrictive strain. It is also known that compressive prestress of the magnetostrictive material caused by applying a force thereto before a magnetic field is applied will align magnetic moments to affect magnetostriction by positioning the magnetic moments so as to lie perpendicular to the direction of the stress and the applied magnetic field parallel thereto. It is therefore an important object of the present invention to provide magnetostrictive material with improved electrical energy transformation efficiency in a wide variety of applications such as transducers, diver communication systems, ultrasonic devices, vibration control and hearing aids, by providing a maximizing degree of annealing under compressive prestress.